In recent years there has been considerable interest in intravenous delivery pumps, particularly for the feeding of saline solutions, whole blood, or the like, to a patient. For many years such materials were fed to a patient only by the force of gravity which necessitated the placing of a container containing the liquid for delivery to a patient at a considerable elevation above the patient. Such a procedure involves frequent checking by a competent person to see that the apparatus was actually feeding the material at the desired rate, as due to the small amount introduced per minute there was frequent clogging of the delivery tube or needle which is used to deliver the material into the vein of the patient. Regulation of flow could only be secured by counting drops of fluid in a predetermined period of time and then figuring the amount delivered per minute. It was found that it was difficult to maintain a regulated flow over a prolonged period of time. Within the past few years, several efforts have been made to provide an accurate pump which would positively deliver the feeding solution to the patient. This necessitates a pump system of extreme accuracy as well as one which will be completely sterile at all times. Such pumps have the advantage that they do not require the placing of the bottle of material to be fed to the patient at a considerable distance above him. They should be very accurate in their delivery and should be readily adjusted. The difficulties with pumps in the past have been, for the most part, too, that they were subject to slight variations in the quantity of material delivered, so that absolute accuracy was still impossible. Also, they are rather expensive to manufacture so that they could not be sold at a price which would permit them to be used once and then thrown away, and were difficult to disassemble, sterilize and reassemble under sterile conditions. In my application, Ser. No. 431,753, filed Jan. 8, 1974 abandoned in favor of application Ser. No. 556,549 which was abandoned in favor of application Ser. No. 704,540, I propose a pump in which these difficulties have been removed by utilizing a pump in which the pumping chamber was always full of the fluid to be pumped and the pumping force was secured by the projection of a plunger into the body of fluid -- the amount of projection being controllable within certain limits and the number of operations per unit of time being also adjustable. In this invention, the plunger was enclosed in a tightly fitting sheath which prevented the entrance of air between the sheath and the plunger, the sheath being sealed to the wall of the pumping chamber so that an air-tight seal or germ barrier was provided between the outside atmosphere and the interior of the pumping chamber.
Associated with such a pump was a driver, such as that disclosed in my patent, U.S. Pat. No. 3,798,982, patented Mar. 26, 1974, in which an arm (97 in said patent) was rocked to depress the plunger and project it into the interior of the pumping chamber. In this patent it was explained how the number of times arm 97 was rocked per unit of time was controlled by the operation of one of a number of cams (51 to 72 in said patent) and the length of each stroke was controlled by the setting of a number of setting members (set screws 111 in said patent). The present invention relates to the combination of the pump of said application, briefly described in said patent, and the actuator of said patent modified as hereinafter described. Such an alarm system is operative when any of three conditions exist: (a) when the supply of material to the pump is shut off or even partially closed, as by the accidental closing of the manual clamp that is normally placed on the outlet tube from the supply container material, the inlet tube is disconnected from the source of supply, and the like; (b) when the supply in the container is exhausted; or (c) when for some reason (such as leakage in the pump, breakage of the sheath enclosing the plunger, or the like) there is less fluid delivered to the pump than specified by the actuator setting. The use of this alarm system permits the operator to exchange bottles of material to be fed to the patient without the admission of any air into the pumping system, so all that is necessary is to remove the conventional hollow needle at the inlet end of the inlet tube from the rubber stopper of the bottle and its immediate insertion into another.